1. Field of the Invention
Embodiments of the present invention generally relate to fabrication of semiconductor substrates, and more particularly, to plasma chambers having a confinement ring configured to confine plasma inside the chambers.
2. Description of the Related Art
Generally, a plasma reactor is used to process semiconductor substrates to produce microelectronic circuits. The reactor forms a plasma within a chamber containing the substrate to be processed. One of the processes that is used is a dry etch process, which typically operates within a vacuum vessel to allow the use of RF plasma conditions, to contain the reactive gases necessary for this process, and to prevent atmospheric contamination of the sample during processing. Chambers in such reactors are typically fabricated from aluminum or stainless steel and, as such, represent a potential contamination source. Other possible drawbacks to exposure of the vacuum vessel to plasma conditions include the cost of parts wear-out, defect issues from deposited polymeric species, and variability in the RF current paths. For these reasons, several approaches have been taken by etch system manufacturers to limit the extent of the plasma to a central region within the vacuum vessel and, in this way, segregate the functions of vacuum and plasma containment. This constraint on the extent of the plasma has generally been termed “confinement” of the plasma.
One approach for plasma confinement is to increase the lifetime of electrons to enhance the plasma efficiency by applying magnetic fields in magnetically enhanced reactive ion etch (MERIE) plasma reactors. While this approach allows the confinement of electrons, both ionic species and radical neutrals often interact with chamber walls, thereby causing contamination sputtering and defect issues from polymer build-up.
Therefore, a need exists for an improved apparatus to confine plasma within a processing region inside the plasma chamber.